Liquid fuel pumping apparatus for supplying fuel to an internal combustion engine

ABSTRACT

A fuel injection pump having a plurality of pumping plungers mounted in separate bores and actuated by individual cams the plungers being moved inwardly by the lobes of the cams to discharge fuel from the pumping chambers through valve controlled outlets, each bore having a spill opening which at a predetermined position during the inward movement of each plunger, communicates with the pumping chamber to terminate the flow of fuel through the outlet. Each spill opening is closable by a valve for the purpose of providing an excess of fuel and the flow of fuel into each pumping chamber is controlled by a common throttle valve.

United States Patent Inventors Dorian Farrar Mowbray Burnharn; KennethAlbert Walters Kemp, Ealing, England Appl. No. 796,315

Filed Jan. 31, 1969 Patented May 18, 1971 Assignee C.A.V. LimitedLondon, England Priority Feb. 1, 1968 Great Britain 5138/68 LIQUID FUELPUMPING APPARATUS FOR SUPPLYING FUEL TO AN INTERNAL COMBUSTION ENGINE 6Claims, 5 Drawing Figs.

US. Cl 417/206, 417/253, 417/495 Int. Cl. ..F04b 23/12, F04b 25/00, F04b39/10 Field of Search 103/2, 2

(.1), 154, 41, 41.1, 41 (S), 169; 418/205, 206, 248, 253, 293, 294, 495(inquired) [56] References Cited UNITED STATES PATENTS 3,071,074 1/1963Bessiere 103/2(.1)UX 3,309,996 3/1967 Rosselli 103/41 3,312,209 4/1967Chmura.... 103/2X 3,313,282 4/1967 Dreisin.... 103/41X 3,385,221 5/1968Parks 103/41 3,396,663 8/1968 Bratten 103/4 1X 3,433,159 3/1969 Kemp103/2 3,438,327 4/1969 Thompson 103/41 Primary ExaminerCarlton R. CroyleAssistant Examiner.lohn J. Vrablik Attorney-Holman, Glascock, Downingand Seebold ABSTRACT: A fuel injection pump having a plurality ofpumping plungers mounted in separate bores and actuated by individualcams the plungers being moved inwardly by the lobes of the cams todischarge fuel from the pumping chambers through valve controlledoutlets, each bore having a spill opening which at a predeterminedposition during the inward movement of each plunger, communicates withthe pumping chamber to terminate the flow of fuel through the outlet.Each spi1l opening is closable by a valve for the purpose of providingan excess of fuel and the flow of fuel into each pumping chamber iscontrolled by a common throttle valve.

LIQUID FUEL PUMPING APPARATUS FOR SUPPLYING lFUlEL TO AN INTERNALCOMBUSTION ENGINE This invention relates to liquid fuel pumpingapparatus for supplying fuel to an internal combustion engine and hasfor its object to provide such an apparatus in a simple and convenientform.

One example of a liquid fuel pumping apparatus in accordance with theinvention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a sectional side elevation of the apparatus,

FIG. 2 is a sectional plan on the line A-A of FIG. 1,

FIG. 3 is a sectional end elevation generally on the line C'C of of FIG.1,

FIG. 4 is a section on the line B-B of FIG. 3, and

FIG. 5 is anend view of the apparatus of FIG. 1 with parts removed forthe sake of clarity.

Referring to the drawings there is provided a body part consisting of anupper portion 11 and an integral lower portion 12. The lower portion isprovided with a bore which extends the full length of the body part andin which is mounted a cam shaft 14. The cam shaft is provided with threecams 15 at axially spaced intervals and each cam has three angularlyspaced lobes 16 which cooperate with the wall of the bore to act asbearings for the cam shaft. At one end the bore is closed by an endclosure 17 through which an extended end of the cam shaft extends. Thisextended end of the cam shaft is adapted for connection to the enginewith which the apparatus is associated and for mounting the apparatus onthe associated engine the end closure which is retained relative to thebody part by bolts 18, is provided with a flange 19. In order to preventescape of fuel along the shaft a seal 20 is provided in the housing.

The other end of the cam shaft mounts the rotary part of a vane type'feed pump indicated at 22. The inlet of the feed pump is incommunication with an inlet chamber 23 and provided in this chamber, isa spring 24 which acts to urge the port block of the pump into contactwith the rotor. Fuel flows to the inlet chamber by way of a fuel inlet25. The fuel inlet 25 is connected by way of a filter element 28 and apair of nonreturn valves 26 and 27 to an inlet 29. Also provided is apriming pump 30 which incorporates a spring loaded pumping element 31which is manually operable and which when depressed forces fuel from itspumping chamber past the nonretum valve 26. When the pumping elementmoves under the influence of its spring the nonreturn valve 27 opens topermit fuel to flow into the pumping chamber of the priming pump readyfor the next pumping stroke thereof.

Formed in the upper portion 11 of the body part are three bores whichare aligned with the earns 15 respectively. Each bore accommodates apumping plunger 41 the lower ends of which bear against roller shoes 42respectively the latter supporting rollers 43 respectively forcooperation with the cam lobes 16. The roller shoes 42 are guided by theopposed surfaces 44 respectively of a slot which is formed in the bodypart and means is provided to prevent axial movement of the rollers.Considering firstly the roller which cooperates with the center camthere is provided at opposite ends respectively of the roller a locatingmember 45. Each locating member is of generally rectangular form havinga curved surface at its lower end which cooperates with a cylindricalsurface 46 fonned on the cam shaft intermediate adjacent cams. The upperportion of the locating member is provided with a slot 47 to receive anear 48 formed on the adjacent end of the roller shoe and in this mannerthe locating members are retained from angular movement about the axisof rotation of the cam shaft and they prevent axial movement of theroller. A similar locating member 45 is provided at the left-hand end ofthe cam shaft this locating member being slidable upon a cylindricalportion of the cam shaft which is positioned between the adjacent cam 15and a pulley 50 the purpose of which will be described. At the oppositeend of the cam shaft the locating member 51 is of annular form buthaving a projecting tongue in which the slot 47 is defined. The bases ofthe slots 47 constitute stops for the ears 48 and the arrangement issuch that at the lowermost position of the plungers the rollers leavethe surface of the cam to permit relubrication of the cooperatingsurfaces. The gap is very small and is too small to show on thedrawings.

The open ends of the bores 40 are closed by delivery valves respectivelyindicated at 52 in FIG. 3 each delivery valve comprises a body portion53 which at one end is screw threaded for mounting in the upper portion11 of the body part and which at its other end defines a pipe connectionwhereby a pipe may be secured thereto. In use the pipe is connected atits other end to a fuel injection nozzle unit incorporating a springloaded control valve. The body portion 53 is provided with a steppedbore 54 and slidable within the bore 40 is a plug 57 also incorporatingan axial passage. The plug is provided with a peripheral flange whichengages with the step in the bore 54 to limit the extent of movement ofthe plug. The end of the passage in the plug adjacent the body portion53 defines a seating with which cooperates a valve element 56 which isloaded by a coiled compression spring 55. In use, as fuel is expelledfrom the bore 40 the plug 57 together with the valve element 56 moveagainst the action of the compression spring until further movement ofthe plug is prevented. During this time fuel flows to the pipe butcontinued flow of fuel from the bore 40 lifts the valve element 56 fromits seating. When the flow of fuel from the bore 40 ceases the valveelement 56 closes onto its seating and the plug together with the valveelement return to the position in which they are shown in the drawingunder the action of the coiled compression spring 55. During thismovement a predetermined quantity of fuel flows from the pipe.

Each bore 40 is provided with a circumferential groove 58 and thegrooves 58 are in communication with each other and also with a passage59. The passage 59 is controlled by a manually operable valve 60 so thatflow of fuel through the passage 59 can be controlled as desired.Furthermore, each bore 40 is provided with a second annular groove 61and again the grooves 61 are in communication with each other and with apassage 62 FIG. 2 which terminates in a port 63 formed in the wall of abore 64. The axis of the bore 64 is disposed parallel to the axis ofrotation of the cam shaft and mounted within the bore is a throttlevalve 65 having a groove 66 formed on its periphery and disposedintermediate its ends. The groove 66 is in communication with a passage67 which communicates with the outlet of the feed pump 22. Moreover, forcontrolling the outlet pressure of the feed pump a spring loaded reliefvalve 68 is provided this being illustrated in FIG. 4. The throttlevalve is urged in one direction by the action of a governor spring 69and movement in this direction increases the effective opening of theport 63. Movement of the throttle valve in the opposite direction isaccomplished by a centrifugally operable mechanism 70 which is driven bymeans of a belt 71 from the pulley 50.

The governor spring comprises a first relatively strong spring 72 and asecond relatively weak spring 73. The two springs are separated by anabutment member 74 which is a cup-shaped form and is slidable on theinternal periphery of a cup shaped part 75 which is mounted for slidingmovement in a wider portion of the bore 64. The position of thecup-shaped part 75 is controlled by an operator adjustable member 76which is operable from the exterior of the apparatus.

Each plunger 41 is provided with a blind stepped bore 80 the wider endof which extends from the end of the plunger remote from the cam shaft.The narrower end of the bore is in communication with a circumferentialgroove 81 which is formed on the periphery of the plunger. Furthermore,the step defined between the wider and narrower portions of the bore 80defines a valve seating for a ball valve 82, and the extent of movementof the ball valve away from its seating is controlled by a pin 83. Thewider portion of the bore 80 is also in communication with acircumferential groove 84 formed on the periphery of the plunger.

The operation of the apparatus will now be described considering plungermovement from the position shown in FIG. 3. As the cam shaft rotatesinward movement of the plunger 41 will occur as the roller 43 rides uponto the cam lobe 16. During the initial movement of the plunger fuelwill be expelled from the pumping chamber which is defined intermediatethe plunger and the plug, through the passage 59 this is of courseassuming that the valve 60 is open. When the end of the plunger coversthe groove 58, fuel will flow through the axial passage in the plug 57as described and injection of fuel will take place to the engine. Thisinjection of fuel continues until the groove 84 registers with thegroove 58 and at this point providing the manually operable valve 60 isopen the remaining fuel in the pumping chamber escapes therefrom by wayof the passage 59. During the inward or upward movement of the plungerthe ball valve 82 is in sealing engagement with the seating. At alltimes during the movement of the plunger the grooves 61 and 81 are inregister with each other and at the end of the inward movement of theplunger and when the roller 43 has cleared a cam lobe 16 fuel underpressure will flow into the bore 80 past the ball valve 82 by way of thegrooves 81 and 61, the passage 62, the port 63 and the groove 66 fromthe outlet of the feed pump. The quantity of fuel which flows dependsupon the effective opening of the port 63. The flow of fuel as describedcauses the plunger to move towards the position in which it is shown inFIG. 3 and if the port 63 is fully open the plunger will actually assumethe position in which it is shown in FIG. 3. if the opening of the port63 is reduced, the plunger will not have time to reach the position inwhich it is shown. In HO. 3, the plunger is shown in the position inwhich the normal maximum quantity of fuel is delivered to the engine butifthe manually operable valve 60 is closed fuel will be unable to escapethrough the passage 59 both at the beginning and at the end of thestroke of the plunger. The result of this is that an excess of fuel willbe supplied to the engine for starting purposes only. The manuallyoperable valve 60 although it can be moved to a closed position by theoperator will automatically be moved to an open position by means notshown, once the engine has started.

The opening of the port 63 is controlled in part by the mechanism 70 andin part by the operator adjustable member 76. The mechanism 70 inconjunction with the governor springs 72 and 73 acts as a speedsensitive governor of a wellknown type. As the speed at which the engineoperates increases then with a given setting of the member 76 thesprings 72 and 73 will be compressed thereby reducing the opening of theport 63. Conversely if the speed decreases the opening of the port 63will be increased thereby increasing the quantity of fuel which issupplied to the engine.

It will be noted that the relief valve 68 allows fuel to discharge fromthe passage 67 into the various chambers defined in the apparatus. inparticular it allows fuel to discharge into the bore in which the camshaft is accommodated. This fuel acts as the lubricant and coolant forthe various working surfaces and additionally acts to cool the drivingbelt 71. Surplus fuel is returned to the fuel inlet by way of a springrelief valve 90 which is located in the housing 21 which accommodatesthe various fuel supply passages and which also carries the priming pumpand the filter. in addition the cavity within the housing 21 is providedwith a bleed 91 through which a restricted flow of fuel takes place to adrain which is conveniently, the fuel tank. This drain allows for theescape of any air or vapor which may collect in the upper portion of thechamber.

In order to stop the engine with which the apparatus is associated ashut off valve 86 provided this being operable from the exterior of thepump and sewing to control communication between the outlet of the feedpump and the port 63. It is to be noted however that the shut off valveis disposed downstream of the relief valve so that when it is closed andbefore the engine has stopped, excessive pressures will not be developedat the outletpf the feed pump.

The apparatus described has the particular advantage that no springs arerequired to effect the return motion of the pumping plungers. Theabsence of the springs removes the problem of corrosion which occurs onthe springs and seriously reduces their life.

Having thus described our invention what we claim as new and desire tosecure by Letters Patent is:

We claim:

1. A liquid fuel pumping apparatus for supplying fuel to an internalcombustion engine and comprising a body part, a plurality of boresdefined in the body part, outlets from pumping chambers at one end ofthe bores, plungers slidable within the bores, cam means for effectinginward movement of the plungers towards said one end of the boresthereby to discharge fuel through said outlets, each cam means includinga cam having a plurality of lobes, a drive shaft rotatable within thebody part, each cam being mounted on the drive shaft, the cam lobescooperating with the wall of a bore within the body part to definebearings for the shaft, inlet conduits formed in the body part andplungers, said conduits communicating with a source of fuel underpressure and with the pumping chambers, nonretum valves in said conduitsrespectively, said nonreturn valves serving to prevent flow of fuelthrough said conduits during the discharge of fuel from the respectivepumping chambers, a throttle valve for controlling the rate of flow offuel from said source to the pumping chambers during movement of theplungers away from said ends of the bores, spill openings in the wallsof said bores, grooves on the plungers respectively for cooperation withsaid openings, said grooves communicating with the pumping chamber andserving at predetermined positions during movement of the plungerstowards said ends of the bore to terminate the delivery of fuel throughsaid outlets, and valve means operable to prevent flow of fuel throughsaid spill openings to enable the apparatus to deliver an excess of fuelfor starting purposes.

2. A pumping apparatus as claimed in claim 1 including rollers forcooperation with the cams respectively, means being provided to separatethe rollers from the cams during rotation of the shaft thereby tofacilitate lubrication of the working surfaces.

3. A pumping apparatus as claimed in claim 2 including shoes carryingthe rollers respectively, each shoe defining ears which project beyondthe ends of the respective roller and which engage in slots respectivelyformed in a pair of locating pieces accommodated in the body part, thelocating pieces acting to locate the roller at the bases of the slotsserving as stops to limit the movement of the roller.

4. A pumping apparatus as claimed in claim 3 including a centrifugallyoperable mechanism for varying the setting of said throttle valve saidmechanism being driven from said shaft by means ofa belt.

5. A pumping apparatus as claimed in claim 4 including a governor springacting on said throttle valve so as to increase the flow of fuel throughthe conduits in opposition to the force exerted by the centrifugallyoperable mechanism, manually operable means being provided to enable theforce exerted by the governor spring to be adjusted.

6. A pumping apparatus as claimed in claim 5 in which the shaft carriesthe rotary part of a fuel feed pump, the fixed part of the feed pumpbeing carried by the body.

2. A pumping apparatus as claimed in claim 1 including rollers forcooperation with the cams respectively, means being provided to separatethe rollers from the cams during rotation of the shaft thereby tofacilitate lubrication of the working surfaces.
 3. A pumping apparatusas claimed in claim 2 including shoes carrying the rollers respectively,each shoe defining ears which project beyond the ends of the respectiveroller and which engage in slots respectively formed in a pair oflocating pieces accommodated in the body part, the locating piecesacting to locate the roller at the bases of the slots serving as stopsto limit the movement of the roller.
 4. A pumping apparatus as claimedin claim 3 including a centrifugally operable mechanism for varying thesetting of said throttle valve said mechanism being driven from saidshaft by means of a belt.
 5. A pumping apparatus as claimed in claim 4including a governor spring acting on said throttle valve so as toincrease the flow of fuel through the conduits in opposition to theforce exerted by the centrifugally operable mechanism, manually operablemeans being provided to enable the force exerted by the governor springto be adjusted.
 6. A pumping apparatus as claimed in claim 5 in whichthe shaft carries the rotary part of a fuel feed pump, the fixed part ofthe feed pump being carried by the body.